大氣電漿噴射製程中氧化鋅與氫摻雜氧化鋅薄膜特性之比較研究

Abstract

本研究以大氣壓電漿噴射製程（Atmospheric Pressure Plasma Jet, APPJ）製備氧化鋅（ZnO）與氫摻雜氧化鋅（ZnO:H）薄膜，探討不同氣體流量條件下薄膜之成長行為、微結構、光學與電學特性變化，並進一步釐清氫在 APPJ 製程中對 ZnO 薄膜之實際作用。過去本實驗室於鎵摻雜氧化鋅（Ga-doped ZnO）薄膜研究中曾觀察到，在氫氣與氬氣的混合載氣條件下，薄膜導電性可獲得提升；然而，由於當時未能有效分離氫氣與氬氣的個別效應，因此氫對薄膜性質改善之具體貢獻仍未明確。本研究遂回歸 ZnO 系統，藉由設計不同氣體條件進行對照，建立氫摻雜效應與薄膜特性之間的對應關係。 本研究所使用之 APPJ 系統具備常壓操作、低溫製程與高鍍率等優點，並以氮氣作為主氣，搭配氬氣與氫氣之不同流量比例進行薄膜沉積。為比較不同氣體條件對薄膜性質之影響，樣品後續分別進行膜厚量測、掃描式電子顯微鏡（SEM）、X 光繞射分析（XRD）、紫外–可見光光譜分析（UV-Vis）、霍爾量測（Hall measurement）等表徵。 實驗結果顯示，不同氣體流量條件會顯著影響 ZnO 薄膜之成長型態與材料特性。SEM 結果指出，純氮氣條件下薄膜表面主要由細小且緻密之顆粒堆疊而成；加入氬氣後，膜層均勻性提升，表面與截面形貌趨於平整；進一步導入氫氣後，薄膜逐漸由原本較均勻之堆疊型態轉為較具方向性之縱向成長結構，且當氫氬混合氣體中氫氣比例提高時，表面晶粒粗化、片狀團聚與柱狀生長特徵更為明顯。XRD 分析顯示，各組樣品皆維持 ZnO 六方纖鋅礦結構，並以 (002) 晶面為主要優選取向；隨氣體條件改變，其繞射峰位置、半高寬、晶粒大小與 c 軸晶格常數亦隨之變化，顯示氫參與成長後確實影響薄膜之結晶結構與微觀排列。光學量測結果則顯示，各樣品皆維持良好可見光穿透性，具備透明導電薄膜之基本光學條件。 在電學性質方面，霍爾量測顯示含氫樣品之載子濃度與遷移率皆較未摻氫樣品提升，導致電阻率明顯下降，顯示氫的導入有助於改善 ZnO 薄膜之導電特性。綜合結構、形貌與電性分析結果可知，氫在 APPJ 製程中不僅可能作為淺層施主提升自由載子濃度，亦可能透過缺陷鈍化與成長動力學調控，進一步改善薄膜之結晶品質與載子傳輸能力。 整體而言，本研究證實氫可在 APPJ 製程中有效摻入 ZnO 薄膜，並對其成長行為、微結構與電學特性產生顯著影響。相較於以往難以明確區分氫氣與氬氣效應的研究結果，本研究藉由純 ZnO 系統與多組氣體條件對照，清楚地釐清了氫在 APPJ 製備 ZnO 薄膜中的角色，並建立不同氣體條件與薄膜特性變化之對應關係，可作為後續透明導電薄膜製程最佳化與應用發展之參考。

In this study, zinc oxide (ZnO) and hydrogen-doped zinc oxide (ZnO:H) thin films were fabricated by an atmospheric pressure plasma jet (APPJ) process. The effects of different gas flow conditions on the growth behavior, microstructure, optical properties, and electrical characteristics of the films were systematically investigated in order to clarify the role of hydrogen in APPJ-grown ZnO thin films. In our previous work on gallium-doped zinc oxide (GZO) thin films, improved conductivity was observed under mixed hydrogen and argon carrier gas conditions. However, because the individual effects of hydrogen and argon could not be clearly separated, the specific contribution of hydrogen remained unclear. Therefore, this study returned to the pure ZnO system and established comparative gas conditions to examine the influence of hydrogen incorporation on thin-film properties. Nitrogen was used as the main gas, while argon and hydrogen were introduced at different flow ratios during deposition. The films were characterized by thickness measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), and Hall measurement. The results showed that gas flow conditions significantly affected the growth mode and material properties of the ZnO thin films. SEM observations revealed that pure nitrogen conditions produced fine and densely packed grains, whereas the introduction of argon improved film uniformity. With further hydrogen addition, the films gradually changed from a relatively uniform stacked morphology to a more directional vertical-growth structure. At a higher H2+Ar ratio, grain coarsening, flake-like agglomeration, and columnar growth became more pronounced. XRD analysis indicated that all samples retained the hexagonal wurtzite structure of ZnO with a preferred (002) orientation. Variations in diffraction peak position, full width at half maximum, crystallite size, and the c-axis lattice constant were also observed under different gas conditions. Optical measurements showed that all samples maintained good visible-light transmittance. Hall measurements further showed that the hydrogen-containing samples had higher carrier concentration and mobility, resulting in lower resistivity. These results indicate that hydrogen introduced during the APPJ process significantly influences the growth behavior, microstructure, and electrical properties of ZnO thin films. Hydrogen may not only act as a shallow donor to increase the free-carrier concentration, but also improve film quality and carrier transport through defect passivation and modification of growth kinetics. This study provides a clearer understanding of the role of hydrogen in APPJ-fabricated ZnO thin films and may serve as a reference for the optimization of transparent conductive thin films.